The purpose of this renewal application is to extend this investigation of intergenerational continuity and discontinuity in drug use in a three-generation (G1, G2, G3) prospective design, using data from the Rochester Youth Development Study (RYDS) and the Rochester Intergenerational Study (RIGS). Drug use is a serious and persistent health problem in American society with a host of negative consequences including increased risk for HIV/AIDS, cognitive impairment, and morbidity. Three aims are addressed to better understand its origins: 1) describe intergenerational continuity and discontinuity across three generations for drug use and related problem behaviors, at both the same and different developmental stages; 2) identify mediating and moderating processes that help account for both intergenerational continuity and discontinuity in drug use; 3) examine the intergenerational influence of G2 fathers as well as G2 mothers. The focal participant is the oldest biological child (G3) of the original participant in the RYDS study. The project proposed capitalizes on the rich developmental data collected since 1988 on the G2 parents and G1 grandparents; combining those data with the prospective data collected in the current study provides a rare opportunity to examine how the parent's own developmental course influences their transition to adulthood and their behavior as parents which, in turn, can be used to explain the onset and development of the G3 child's drug use. In Year 1 (1999), 370 G3 children (age 2 and older) and their parents were enrolled; new 2-year-olds are added each year. By Year 21, the last assessment proposed, a total of 542 G3 families will have enrolled in the study-99% of the sampling goal of all oldest biological G3 children. Annually, interviews are conducted with the G2 parent, the G3 child (age 8 and older), and, in the G2 father families, the child's bio-mother (93%) or another primary caregiver (7%). Measures include the parent's structural position and stressors, drug use and problem behaviors, prosocial bonds, peer networks, family context, and parenting behaviors. G3 assessments include their general psychosocial development, with detailed information on the onset and course of their drug use, other problem behaviors, and prosocial competencies. The extension of data collection through Year 21 that is proposed here is particularly crucial to realize the full potential of the project because it is during these years hat 1) the vast majority of the G3 children will move through adolescence and into early adulthood when drug use reaches its peak, 2) G3 overlaps in age with the G2 parents when they were assessed in the original study, and 3) the prevalence and frequency of G3 drug use are high enough to support detailed analyses of the Aims. The findings will yield crucial insights into the onset and course of G3 drug use that have the potential to generate early and novel approaches to drug use prevention.